Try switching the CPU usage from "low" or "normal" to "high". If this doesn't help, you might have some other applications running which use too much of the CPU power - or your CPU is not fast enough. The more instruments you have running at the same time, the more CPU power the software will require. So reducing the amount of meters running simultaneously might be a solution for that problem, too.

Since PG-AMM is using OpenGL you should always install the latest graphics driver for your GPU!